Dual sweep design for manufacturing polycrystalline diamond compact

ABSTRACT

A method for forming a polycrystalline diamond compact (PDC) includes steps of disposing a first catalyst source on a top of a plurality of diamond crystals; disposing a second catalyst source at a bottom of the plurality of diamond crystals; and applying high temperature and high pressure to the plurality of diamond crystals, the first catalyst source and the second catalyst source such that the plurality of diamond crystals are sintered into a polycrystalline diamond compact.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of, and claiming priorityunder 35 U.S.C. §120 to U.S. patent application Ser. No. 13/755,589,filed on Jan. 31, 2013.

FIELD OF THE DISCLOSURE

The present application relates to a polycrystalline diamond compact(PDC), and more particularly, to a PDC having a polycrystalline diamondsintered on a carbide substrate using a sweep-through process.

BACKGROUND

In the discussion that follows, reference will be made to certainstructures and/or methods. However, the following references should notbe construed as an admission that these structures and/or methodsconstitute prior art. Applicant expressly reserves the right todemonstrate that such structures and/or methods do not qualify as priorart against the present invention.

Twist drills and other tools used in the drilling industry often use apolycrystalline diamond compact (PDC). Commonly, a PDC is made using ahigh pressure and high temperature (HPHT) sweep-through process. FIG. 1is a cross-sectional view showing formation of a PDC in accordance witha related art HPHT sweep-through process. As shown in FIG. 1, in thesweep-through process for forming a PDC, a mass of diamond crystals isplaced into a refractory metal container. The diamond mass may containsome binder material or additives blended in to promote sintering.Cemented carbide (WC—Co composite hard metal) substrate is placed in thecontainer such that a surface of the substrate touches the mass ofdiamond crystals. The assembly is then subjected to HPHT conditions.Typically, the binder material present in the substrate melts and sweepsinto the mass of diamond crystals. In the presence of the liquid bindermaterial, diamond crystals bond to each other by adissolution-precipitation process to form a polycrystalline diamond massattached to the cemented carbide substrate.

The carbide substrate usually includes small amounts of a bindermaterial, such as cobalt, nickel, iron or their alloys, to improveintegrity and strength. The binder material is generally selected tofunction as a catalyst for melting and sintering the diamond crystals.That is, as shown in FIG. 1, in existing processes for forming a PDC,the cobalt or other binder material from the substrate will melt underHPHT conditions from the carbide substrate and “sweep” across thediamond powder to create the PDC. Here, the sweep occurs as a front thatmoves from an interface between the carbide substrate and the diamondcrystals toward a distal surface of the diamond. If the interfacebetween the carbide substrate and the diamond is planar, the sweep maybe uniform.

However, in many PDC arrangements, such as those for twist drills, thecarbide substrate may define a non planar interface with the diamondcrystals. For example, deep valleys may be defined in the carbidesubstrate with the diamond crystal disposed therein. Because of thegeometry of such interfaces, the sweep pattern is irregular.Accordingly, the irregular sweep front may result in areas of poorlysintered diamond (a defect zone), especially in area near the cuttingedge of the PDC. Moreover, metal filled cracks or fingers may form inthe sintered diamond near the carbide substrate due to the irregularsweep pattern when the related art sweep-through process is applied.

Accordingly, there is a need to provide a controlled and uniform sweeppattern to prevent irregularities even with non planar carbidesubstrates. In addition, there is a need to control the substrateproperties and diamond properties without affecting each other possiblyby providing an alternate binder material chemistry than that in thecemented carbide substrate.

SUMMARY

Accordingly, the present invention is directed to an arrangement forforming a polycrystalline diamond compact (PDC) that substantiallyobviates one or more of the problems due to limitations anddisadvantages of the related art.

An embodiment of a polycrystalline diamond compact (PDC) is provided inwhich defects and irregularities are minimized or prevented. Anotherembodiment controls a sweep pattern in forming a polycrystalline diamondcompact (PDC). In a further embodiment, a polycrystalline diamondcompact (PDC) is provided with an improved cutting edge and reducedcosts.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, a methodfor forming a polycrystalline diamond compact (PDC) includes disposing afirst catalyst source on a first side of a plurality of diamondcrystals; disposing a second catalyst source at a second side of theplurality of diamond crystals; and applying high temperature and highpressure to the plurality of diamond crystals, the first catalyst sourceand the second catalyst source such that the plurality of diamondcrystals are sintered into a polycrystalline diamond compact.

In another embodiment, a method for forming a polycrystalline diamondcompact (PDC) may comprise steps of disposing a first catalyst sourceand a second catalyst source near a plurality of diamond crystals; andsweeping the plurality of diamond crystals with the first catalystsource and the second catalyst source at high temperature and highpressure to form polycrystalline diamond.

In further another embodiment, a polycrystalline diamond compact maycomprise a plurality of sub-micron diamonds; and a sintered catalyst,wherein a thickness of the polycrystalline diamond compact is more than1.5 mm, wherein the polycrystalline diamond compact does not have adefect zone.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are explanatory and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWING

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 is a cross-sectional view showing formation of a polycrystallinediamond compact (PDC) in accordance with a related art sweep-throughprocess;

FIG. 2 is a cross-sectional view showing an polycrystalline diamondcompact (PDC);

FIG. 3 is a flowchart showing a method of making polycrystalline diamondcompact;

FIG. 4 is schematic diagram showing cross-sectional views to illustratethe arrangement used in a sweep-through process according to anembodiment;

FIGS. 5 and 6 are schematic views showing different arrangements ofcarbide substrates having non-planar surfaces in accordance withembodiments;

FIGS. 7-11 are SEM images showing the depth of the leach layers as afunction of leach time using an aqua regia solution;

FIG. 12 is a graph summarizing the relationship between leach depth andleach time for the SEM images of FIGS. 7-11;

FIG. 13 is a flowchart showing a method of making polycrystallinediamond compact according to an embodiment;

FIG. 14 is a schematic diagram illustrating a dual sweep designaccording to one embodiment;

FIG. 15 is a flowchart showing a method of making polycrystallinediamond compact according to another embodiment;

FIG. 16 is a graph illustrating a wear rate comparison between thestandard solid core and dual sweep solid core polycrystalline diamond;and

FIG. 17 is a schematic diagram illustrating a dual sweep designaccording to another embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to preferred embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. The detailed description of preferred embodimentscan be read in connection with the accompanying drawings in which likenumerals designate like elements.

FIG. 2 is a cross-sectional view showing a polycrystalline diamondcompact (PDC) in accordance with one embodiment of the presentinvention. As shown in FIG. 2, the PDC includes a substrate 201, such ascemented carbide substrate, with a polycrystalline diamond table 203bonded onto a top surface of the substrate 201. The polycrystallinediamond table 203 may initially not have a sweep material from thesubstrate 201. The sweep material may be cobalt, for example. Thecarbide substrate 201 may include tungsten carbide (WC) or othermaterial and has a binder metal doped therein to improve integrity andstrength of the carbide substrate 201. The binder metal may be cobalt orother iron-group element. A PDC is cylindrical shaped tungsten carbidesubstrate with from about 6% to about 15% cobalt therein having adiameter of 10-25 mm and a height of 5-20 mm where the polycrystallinediamond crystal is about 1-4 mm thick, for example. In one embodiment,the sweep material may be mixed with a plurality of diamonds before theplurality of diamonds are sintered onto the polycrystalline carbidesubstrate. In another embodiment, the sweep material may be from acobalt source on the plurality of diamond crystals on a surface of thediamond crystals at a distance from the cemented carbide substrate.

FIG. 3 is a flowchart showing a method of forming a PDC in accordancewith an embodiment of the present invention. FIG. 4 is a schematicdiagram showing cross-sectional views to illustrate an arrangementaccording to a sweep-through process according to the flowchart of FIG.3.

As shown in step 301 of FIG. 3, a carbide substrate is treated with anaqua regia solution to remove the binder metal from a surface portion ofthe carbide substrate. For example, 400 ml of aqua regia including HCland HNO₃ in a 1:3 ratio may be used. The carbide may be completelyimmersed in the aqua regia acid to leach all exposed surfaces of thecarbide substrate. Alternatively, a single surface or a portion of oneor more surfaces may be leached by protecting the rest of the surfacesusing gaskets such as Viton® gaskets or acid-resistant paste, forexample. The leach depth and leach time depends on the acid compositionin the aqua regia, temperature, amount of cobalt being leached andquantity of acid. After a certain time (depending on the parametersmentioned above), the aqua regia solution may get saturated with theleaching byproducts, the tungsten carbide on the surface may separateand go into the solution and the leach depth may stay constant. However,it is desired that a sufficient amount of leaching occurs so that thereis insufficient cobalt or other materials in the surface portion of thecarbide substrate to function as a sweep catalyst during the sinteringprocess. A leaching depth of 20 microns may be sufficient to prevent theremaining binder material in the substrate from melting and sweepinginto the mass of diamond powder during sintering, but more desirably, aleaching depth of 40 microns substantially eliminates the carbidesubstrate as source of sweep material during the sintering process.

After removing the carbide substrate from the aqua regia and cleaningthe carbide substrate, a bed of diamond crystals are packed on the topof the treated carbide substrate as shown in step 303. The diamondcrystals may be generally synthetic diamond in the form of a powder orgrit.

As shown in step 305, a sweep material is disposed on an upper surfaceof the diamond crystal bed. That is, the sweep material is on a surfaceof the diamond bed opposite the carbide substrate. The sweep materialmay be cobalt, nickel, iron or their alloys or other suitable sweepmaterials. The sweep material may contain additives such as chromium orother metals such as cobalt, nickel and iron. Also, the binder metal inthe carbide substrate need not be the same material as the sweepmaterial. By contrast with the related art method, the aqua regiatreatment of step 301 may have leached out any cobalt in the surfaceportion of the carbide substrate. Therefore, a separate sweep materialis provided. The interface between the diamond bed and the sweepmaterial may be planar to facilitate a uniform sweep front during thesintering process. A cup, such as a tantalum cup, or other refractorymetal, may be disposed over the sweep material, diamond crystals, andcarbide substrate to hold the materials in place, as shown for examplein FIGS. 5 and 6. In addition, because the high pressure may be appliedusing a press with salt as the pressure transmitting medium, the cupalso serves to prevent contamination.

Alternative to step 305, the plurality of diamond crystals may be mixedwith a sweep material, such as cobalt. Additive materials, such aschromium, nickel and iron may be added to the mixture of the pluralityof diamond crystals with the sweep material. The mixture of theplurality of diamond crystals with the sweep material and optionaladditive materials may be disposed on the treated cemented carbidesubstrate.

In step 307, the carbide substrate, the diamond crystals and the sweepmaterial may be disposed in a press system so that high temperature andpressure may be applied. The particular parameters may vary byequipment, but parameters for pressure, temperature and time are:pressure may be greater than 50-55 Kbar for diamond to be stable and maybe typically at 70-75 Kbar, 1400-1600° C., 5-10 min; another example ata lower pressure may be 60-65 Kbar, 1400° C.-1600° C., 20-30 min. Inthis manner, the diamond crystals are sintered into a polycrystallinediamond attached to the carbide substrate to form the polycrystallinediamond compact. Of course, additional materials as known in the art maybe included in the sweep materials.

Because the interface between the sweep material and the diamondcrystals is planar, a planar sweep front may be achieved. Thus, problemsassociated with the related art, such as the metal filled cracks/fingersand areas of poorly sintered diamond, may be prevented. Also, the sweepdirection during the sintering process is toward the carbide substraterather than away from the carbide substrate. Therefore, the describedarrangement has the additional advantage of sweeping any contaminantsaway from the upper surface, i.e., the cutting edge. Here, thecontaminants may be present due to a variety of sources, such as calciumfrom processing of the diamond crystals, contaminants within the diamondcrystals that are exposed due to fracturing of the crystals at highpressure. Thus, the sweep direction improves the quality of the cuttingedge. Moreover, a near net (final) shape is obtained, thereby reducingfinishing costs. For example, in the disclosed process, contaminants areswept away from the cutting edge and into a region which does not takepart in the cutting action. So the cutting edge contains well sintereddiamond. In contrast, in prior art, the contaminants end up at thecutting edge, and hence additional finishing steps are necessary such aslapping, grinding etc to remove a portion of the diamond and expose awell sintered cutting edge.

FIGS. 5 and 6 are schematic views showing different arrangements ofcarbide substrates having non-planar surfaces in accordance withembodiments of the present invention. In FIG. 5, the carbide substratehas a raised central portion, and, in FIG. 6, the carbide substrate hasa deep valley. Despite having non-planar interfaces between the carbidesubstrate and the diamond crystals, regular sweep patterns may beachieved using the arrangement of the sweep material and the HPHTprocessing as disclosed herein. FIGS. 5 and 6 also illustrate the use ofa cup, such as a tantalum cup, as described above. Embodiments may havevarious surfaces other than those shown in FIGS. 5 and 6.

FIGS. 7-11 are SEM images showing the depth of the leach layers as afunction of leach time using an aqua regia solution. For each image, 400mL of aqua regia (300 mL HCl and 100 mL HNO₃) was applied at 24° C. to atungsten carbide (WC) substrate having 11.5% cobalt (Co) therein and anexposed surface area of 0.3 in². For each leach time, two carbidesubstrates were used to check consistency. That is, ten carbidesubstrates were put in the aqua regia at the beginning and twosubstrates were taken out at each of the respective times.

FIG. 12 is a graph summarizing the relationship between leach depth andleach time for the SEM images of FIGS. 7-11. As shown in FIG. 12, theleach depth levels off after about 60 minutes of leach time under theconditions described above. It has been found that the sweep-throughprocess resultant from cobalt in the carbide substrates is reduced butnot eliminated when carbide substrates were leached for 20 minutes toachieve a leach depth of 28 microns. In this case, it was found that thesweep from the carbide substrate was sufficiently reduced so that thesweep from the cobalt disk on the diamond achieved before the sweep fromthe carbide substrate, thereby providing improved results as comparedwith the related art. It has also been found that the sweep-throughprocess resultant from cobalt in the carbide substrates wassubstantially eliminated when the carbide substrates were leached for 60minutes or more. Thus, under the specified conditions, it may be desiredto leach the carbide substrates for at least 60 minutes. Moreover, itmay be desired to achieve a leach depth of at least 40 microns.

By removing the cobalt in the layer of the carbide substrate closest tothe diamond and by providing a different sweep source, the arrangementdescribed in this application provides a way of altering and controllingthe sweep pattern in the sweep-through process. As a result, PDCs may beobtained with improved cutting edges and reduced costs while alsopreventing defects and irregularities.

In one embodiment, as shown in FIG. 13, a method 1300 of forming apolycrystalline diamond compact (PDC) may comprise steps of disposing afirst catalyst source on a first side of a plurality of diamond crystalsin a step 1302; disposing a second catalyst source at a second side ofthe plurality of diamond crystals in a step 1304, wherein the first sidemay be an opposite side of the second side of the plurality of diamondcrystals; and applying high temperature and high pressure, such as atleast 45 Kbar and 1400° C. respectively, to the plurality of diamondcrystals, the first catalyst source and the second catalyst source suchthat the plurality of diamond crystals are sintered into apolycrystalline diamond compact in a step 1306. The method 1300 mayfurther include steps of melting the first catalyst source firstly,melting the second catalyst source secondly; sweeping the plurality ofdiamond crystals with the first catalyst source and the second catalystsource to form polycrystalline diamond.

In one embodiment, the first catalyst source and the second catalystsource may have different compositions. In another embodiment, the firstcatalyst source and the second catalyst source may have samecomposition, such as a transition metal catalyst. The transition metalcatalyst may be iron group metal, such as cobalt. In one embodiment, thesecond catalyst may be a cobalt disk. In another embodiment, the secondcatalyst may be cobalt ring, such as 0.05″ thick, 0.99″ OD, 0.716″ ID.In one embodiment, the first catalyst source may have a plurality ofperforated holes. The plurality of perforated holes may be formed aftercemented tungsten carbide is leached by acid. The acid may leach cobaltcatalyst out and leave unfilled pores where the cobalt catalyst used tooccupy. In another embodiment, the second catalyst source may be anunleached cemented tungsten carbide. Because the cobalt solubilizestungsten carbide, the melting point for the cobalt inside the cementedtungsten carbide may have a lower melting point than a pure cobalt diskor ring. So when temperature increases under pressure, the cobalt insidethe tungsten carbide may melt first at lower temperature than cobaltdisk or ring.

To further illustrate the dual sweep method 1300, FIG. 14 shows aschematic diagram of a dual sweep design of polycrystalline diamondcompact 1400 according to one embodiment. During high temperature highpressure period, cobalt disks 1412 on a top 1402 of the plurality ofdiamonds (forming diamond bed 1410 in a tantalum cup 1408) melt andsweep through the diamond bed 1410 under high pressure and temperature.The cobalt ring 1414 at a bottom 1404 of the diamond bed 1410 in the cup1408 may melt and sweep upward on the side of the diamond bed 1410 andtoward a bottom center 1416 of cobalt ring 1414 under high pressurewhile the cobalt disk 1412 from the top 1402 sweeps down through thewhole bed. The cobalt from the top of the diamond bed helps to sweepimpurities of the diamond bed down to the bottom center 1416 and a nosearea 1406, for example. The dual sweep action helps to improve theuniform distribution of Co with the Co ring helping distribution in thebottom zone while the main sweep of Co overlaps dead zone orinsufficiently sintered diamond zone. Any cobalt source with differentsize and geometry may be used as the first or second cobalt source.

In another embodiment, as shown in FIG. 15, a method 1500 of forming apolycrystalline diamond compact (PDC) may comprise steps of disposing afirst catalyst source and a second catalyst source near a plurality ofdiamond crystals, such as the first catalyst source and the secondcatalyst source being at an opposite side of the plurality of diamondcrystals, in a step 1502; and sweeping the plurality of diamond crystalswith the first catalyst source and the second catalyst source at hightemperature and high pressure, such as at least 45 Kbar and 1400° C.,respectively, to form polycrystalline diamond in a step 1504. The method1500 may further include steps of melting the first catalyst sourcefirstly, then the second catalyst secondly; sweeping the plurality ofdiamond crystals with the first catalyst source firstly, then with thesecond catalyst secondly. In one embodiment, the first catalyst sourceis cobalt cemented tungsten carbide and the second catalyst source maybe a cobalt ring. The plurality of diamonds may be any size of diamonds,from 0.1 nm to 1000 microns. In one embodiment, the plurality of diamondis sub-micron diamonds.

A polycrystalline diamond compact may comprise a plurality of sub-microndiamonds and a sintered catalyst, wherein a thickness of thepolycrystalline diamond compact is more than 1.5 mm, wherein thepolycrystalline diamond compact does not have a defect zone. The defectzone, used herein, may refer to areas of poorly sintered diamond. Thedefect zone may normally be seen at the far end of the part from thecobalt source. Allowance for this defect zone may lead to additionalfinishing process and waste volume in the HPHT cell. Tight toleranceparts may be designed that reduces the cost of the finishing processes.The sub-micron diamonds may have sizes less than 0.9 microns, forexample. In one embodiment, the sub-micron diamonds may have sizes fromabout 0.2 microns to about 0.8 microns.

Example 1

Referring again to FIG. 14, the cobalt ring 1414 such as 0.05″ thick,0.99″ OD, 0.716″ ID was dropped into the tantalum cup 1408. The diamondfeeds were poured into the tantalum cup 1408 to form a diamond bed 1410.A cobalt disk 1412 was put on the top of the diamond bed 1410.

This assembly was subjected to HP/HT processing at about 65 Kbar attemperature of about 1400° C. for 10 minutes to form the sinteredsubmicron PCD tool blank 1400. The PCD tool blank 1400 was finished toproduce a diamond layer about 20 mm.

A standard solid core PCD tool blank was made according to aboveprocedure except without the cobalt ring under the diamond bed.

A blast wear test was employed to test the quality of PCD. In the blastwear test, submicron diamond media (average grain size 30 microns) wascarried through a nozzle (having a diameter of 0.5 mm) by air pressure(about 75 psi) to impact the cross-section of a 20 mm thick sample ofPCD at a distance of 1 cm. The sample was held at a 90 degree angle tothe nozzle. The sample was then subjected to the high pressure stream ofthe media for 20 seconds. Weight loss was then measured and convertedinto a wear rate (mg/min). PCD bodies of the present disclosureexhibited similar wear rate as the standard solid core at the distancebetween about 2 mm to about 14 mm from the top cobalt disk 1412 (asshown in FIG. 14). But from about 14 mm to about 18 mm distance from thetop cobalt disk, the dual sweep solid core PCD showed much lower wearrate than the standard solid core product. This indicated that PCD bodyof the present embodiment had better sintered diamonds than the standardsolid core PCD.

Although not harder than polycrystalline diamond, the loose diamondmedia impacts the PCD, introducing defects until pieces can break away.This was directly linked to the quality and degree of sintering of thePCD part. Analysis of the samples is shown in FIG. 16 which compareswear rate and PCD thickness. Dual sweep solid core, prepared accordingthe present disclosed method, shows an improved abrasive wear ratecompared the standard solid core sample.

Example 2

Referring to FIG. 17, similarly to example 1, an assembly of carbide(containing sweep material 1, such as Cobalt), sub-micron diamonds and asecond sweep material (Co with about 3 wt % Fe) contained by a tantalumcup was assembled and subjected to HPHT conditions (about 65 Kbar, about1400° C.) for about 16 minutes.

The sub-micron diamond was swept first by the Co from the carbide (lowermelting point) and secondly by the purer Co (higher melting point) fromthe top. The sweep zones between sweep 1 and sweep 2 overlapped and thedefect zone carbon (from sweep 1) was solubilized by the sweep 2 Cobalt.This rendered a defect free, near net dimension body of sub-micron PCDdiamond of thickness about 5 mm. This thickness might not be achievableby a one-sided sweep for the same materials. Also, the defect zone couldnot be eliminated if the melting points are the same.

To test whether the thicker sub-micron had good quality, the blast test(see description in Example 1) was applied to both sides of thesub-micron part as well as a sub-micron reference standard. Results wereshown in Table 1.

TABLE 1 Sample Wear Rate (mg/min.) Standard Deviation SM Std Side 1 10.60.05 SM Std Side 2 9.3 1.10 SM Thick Side 1 9.2 0.67 SM Thick Side 2 6.90.21

In Table 1 it could be seen that the wear rate of the thick sub-micronPCD was not negatively affected by the dual sweep process and, in fact,on average, the wear rate was improved.

Although the present invention has been described in connection withpreferred embodiments thereof, it will be appreciated by those skilledin the art that additions, deletions, modifications, and substitutionsnot specifically described may be made without department from thespirit and scope of the invention as defined in the appended claims.

What is claimed is:
 1. A method of forming a polycrystalline diamondcompact (PDC), comprising: disposing a first catalyst source on a firstside of a plurality of diamond crystals; disposing a second catalystsource at a second side of the plurality of diamond crystals; andapplying high temperature and high pressure to the plurality of diamondcrystals, the first catalyst source and the second catalyst source suchthat the plurality of diamond crystals are sintered into apolycrystalline diamond compact.
 2. The method of claim 1, wherein thefirst catalyst source and the second catalyst source have differentcompositions.
 3. The method of claim 1, wherein the first catalystsource and the second catalyst source have same composition.
 4. Themethod of claim 1, wherein both the first catalyst source and the secondcatalyst source are cobalt.
 5. The method of claim 1, further comprisingmelting the first catalyst source firstly, melting the second catalystsource secondly.
 6. The method of claim 1, wherein the first side is anopposite side of the second side of the plurality of diamond crystals.7. The method of claim 1, wherein the second catalyst source is a cobaltring.
 8. The method of claim 1, wherein the second catalyst is a cobaltdisk.
 9. The method of claim 1, wherein the first catalyst source has aplurality of perforated holes.
 10. The method of claim 1, wherein highpressure and high temperature are at least 45 Kbar and 1400° C.,respectively.
 11. The method of claim 1, further comprising sweeping theplurality of diamond crystals with the first catalyst source and thesecond catalyst source to form polycrystalline diamond.
 12. A method offorming a polycrystalline diamond compact (PDC), comprising: disposing afirst catalyst source and a second catalyst source near a plurality ofdiamond crystals; and sweeping the plurality of diamond crystals withthe first catalyst source and the second catalyst source at hightemperature and high pressure to form the polycrystalline diamondcompact.
 13. The method of claim 12, wherein the first catalyst sourceand the second catalyst source are at an opposite side of the pluralityof diamond crystals.
 14. The method of claim 12, wherein high pressureand high temperature are at least 45 Kbar and 1400° C., respectively.15. The method of claim 12, wherein the first catalyst source is cobaltcemented tungsten carbide.
 16. The method of claim 12, wherein thesecond catalyst source is a cobalt ring.
 17. The method of claim 12,further comprising sweeping the plurality of diamond crystals with thefirst catalyst source firstly, then with the second catalyst secondly.18. The method of claim 16, further comprising melting the firstcatalyst source firstly, then the second catalyst secondly.
 19. Themethod of claim 16, wherein the plurality of diamonds is sub-microndiamonds.
 20. A polycrystalline diamond compact, comprising: a pluralityof sub-micron diamonds; and a sintered catalyst, wherein a thickness ofthe polycrystalline diamond compact is more than 1.5 mm, wherein thepolycrystalline diamond compact does not have a defect zone.
 21. Thepolycrystalline diamond compact of claim 20, wherein the sub-microndiamonds have particle sizes less than 0.9 microns.
 22. Thepolycrystalline diamond compact of claim 20, wherein the sub-microndiamonds have particle sizes from about 0.2 microns to about 0.8microns.